Woah!
This is increasingly reading the same as a problem that I have with my Moto Morini 125H engine. This uses a Ducati Electronicca alternator, 6v 4 coil charging system, along with a single power coil and a trigger coil, mounted on the alternator stator plate and within the alternator rotor, powering and sending an ignition signal to a CDI/coil unit. The trigger for the trigger coil is inside the rotor.
Your MotoTrans has a similar alternator stator, but you might not be able to view the coils as they may be encapsulated in resin. However, the Saches ignition trigger will be mounted in the upper part of the front offside compartment of the engine timing chest. And the timing is adjusted by moving the trigger in relation to the rotation of the disc on the shaft.
My Morini 125H will readily start and idle all day at 1,100 - 1,200rpm. When the throttle is gradually opened the engine revs will increase to approximately 2,000rpm, at which point the engine starts to hesitate and if the throttle isn't opened any further, this irregular running will continue, but the exhaust pipe will start to glow red hot! If the throttle is gradually opened further, the revs may increase to 2,500rpm, by which time the back firing and spluttering is very pronounced and then the engine will stop dead.
From having spent many hours trying to solve this conundrum, along with other Morini 125H owners suffering exactly the same symptoms, we have proved that the engine timing is not advancing!
Having re-read your post of Thu Sep 28, 2023 7:37 am on this thread, I suspect that you need to be contacting Saches to find answers as to how to establish whether their CDI unit is faulty, or the trigger unit that sends electrical signals to the CDI is faulty.
In my opinion your problem lies with the ignition and not the carburation. By all means check the ignition timing, but in your previous posts you have said
andMy scrambler has been technically ready to go for the last 12 months or so, and it was starting, running and revving well in the garage with no load on the engine. Not road-tested though.
andSo I got her started, warmed-up for a few minutes, then took her out on the road for the first time since 1981. I have some carb tuning to do, as the engine wouldn't run without the choke, was unwilling to rev, and generally seemed gutless.
The gearing is higher than I remembered, so that resulted in a stall, but restarted without problems and I had a sedate circuit of the local roads in first & second gear. It felt like the engine wouldn't tolerate third gear.
On reflection these observations read as though there is a gradual breakdown of an electrical component and very similar to my experience with the 125H. At present all my 125H testing has to be carried out on the stand, as putting any load on the engine causes it to die. At one time the engine wouldn't rev sufficiently to achieve more than 60Km per hour, but this gradually declined, with time and deterioration of the trigger coil internal insulation.
So, I do not think that the engine timing, or the ignition timing are at fault. Something within the ignition components has cried "Enough!", sufficient to stop the ignition advance.
Electrickery is not my forte and with the 125H, the whole of the Morini Riders Club expertise has been brought to bear to try to solve the problem. I believe the problem has been located and it is due to the polarity of the signal coil not sending the correct signal to the CDI circuitry to advance the ignition when the desired engine "RPM" are reached. Hence my advice to go back to Saches. Just because it is a new system, doesn't mean that it doesn't have a component failure!
I hope this helps, good health, Bill